Investigators have said Nolen had just been suspended from his job when he walked into the company's administrative office and attacked Colleen Hufford, 54, severing her head. They say he also stabbed another co-worker, who survived, before he was shot by a company executive.

At Nolen's formal arraignment, he said he wanted to plead guilty in the case, District Attorney Greg Mashburn said.

"He stood up and voiced his wish to plead guilty," said Mashburn, whose office is seeking the death penalty in the case.

Nolen told the judge Thursday he is not interested in seeking either of the two other possible penalties for first-degree murder — life in prison with or without the possibility of parole, the prosecutor said.

Defence attorney Mitch Solomon questioned whether Nolen is mentally competent to enter a guilty plea, Mashburn said. Walked said she wanted to give Nolen and his attorney more time to consider their next step, so she and entered a not guilty plea on Nolen's behalf.

The next hearing is scheduled for May 20. Solomon did not immediately return a telephone call seeking comment on the development.

If Walkley eventually allows Nolen to plead guilty, prosecutors would still have to present evidence at a sentencing hearing to justify a penalty of death in the case, Mashburn said. Nolen's attorneys would have an opportunity to present mitigating evidence on his behalf to support a life sentence, he said.

In October, a judge found Nolen mentally competent to stand trial, rejecting defence attorneys' claims that Nolen was intellectually impaired. And he was ordered to stand trial last month following a preliminary hearing where three employees at the food processing plant provided graphic testimony about the attack, including how Nolen apparently grabbed Hufford, placed a hand on her forehead and sliced her neck with a butcher knife.